1. Field of the Invention
The present invention relates to a printing apparatus that forms an image by reciprocating a carriage mounting a print head and more particularly to an ink jet printing apparatus and an ink jet printing method capable of using a relatively thick print material such as a tray accommodating a compact disc.
2. Description of the Related Art
Ink jet printing apparatus are currently being applied not only to rectangular sheets of paper or strips of rolled paper but also to other print materials having a variety of two-dimensional shapes and thicknesses. For example, even small and thick materials, such as CD-Rs, DVDs and cards, are printed with various images and characters by putting on their surfaces a print material suited for ink jet printing and printing images and characters (in the following, these materials to be printed on are generally called compact discs (CDs)).
In conventional general-purpose ink jet printing apparatus, when a material such as a CD is to be printed, if a general transport path for paper is used, various problems will arise, including bad feeding performance because of its high stiffness, the CD sustaining scores, and the CD failing to be transported because of a relatively long distance between feed rollers. To deal with these problems, the conventional apparatus use a dedicated path for a tray different from the general paper transport path.
Since trays have a greater thickness than that of general paper, the tray transport path is set almost horizontal and, from a standpoint of user's maneuverability, often configured to accept a tray from a front side of the printing apparatus as opposed to a back side from which paper is usually loaded. In this configuration, whether the tray is loaded in the transport path is usually not directly detected by a sensor. This is because the use of a configuration that enables detection of the presence or absence of a tray loaded from the opposite direction makes a reduction in size and cost of the apparatus difficult.
Meanwhile, in ink jet printing apparatus capable of printing such materials as CDs, an ink jet printing method that performs printing by scanning an ink ejecting print head mounted on a carriage along with the carriage is widely adopted. Thanks to many advantages, such as an ease with which an image can be formed in colors and at an increased resolution and low operation noise, the ink jet printing apparatus are in widespread use.
Many ink jet printing apparatus have a print head and an ink tank removably and replaceably mounted on a carriage. In this configuration, when the print head and ink tank are to be removed or replaced, the user opens a cover member of the printing apparatus, automatically causing the carriage to move to a predetermined position for replacement. In some printing apparatus, an opening formed at this replacement position is provided in a housing case. The position where the carriage is dismounted or replaced is often located on a transport path of a print medium such as paper or a tray.
The ink jet printing apparatus generally perform cleaning processing that makes a print head fit for ink ejection operation. The cleaning processing includes a suction operation that sucks out from the print head ink which is unfit for printing due to progressive degradation over time, a preliminary ink ejection operation for a similar purpose, and a wiping operation that wipes ink off an ink ejection portion of the print head. Some apparatus also perform an ink volume check as part of the cleaning processing before starting the printing operation by installing an ink tank sensor to detect a volume of ink in the ink tank.
These cleaning processing operations for the print head are performed either by the user manually requesting the cleaning through the printing apparatus or automatically by the printing apparatus according to a time that has passed from the previous cleaning operation. Of the apparatus that perform the cleaning operation automatically, some execute the cleaning operation prior to the printing operation immediately after the apparatus receives a print command.
These conventional techniques, however, have the following drawbacks.
(1) Of those printing apparatus that print on a print medium, such as a CD placed on a tray loaded into a transport path, some employ a construction in which the tray is loaded from a direction opposite to that in which paper is loaded. In this case, if it is checked not only whether paper is loaded but also whether a tray is loaded, sensors to detect the paper and tray separately must be provided in the printing apparatus. Not only does this make the sensor arrangement difficult but it also hinders a size reduction of the apparatus. Thus, in practice, it is often the case that a detection is not made as to whether the tray is loaded in the transport path. In a configuration that does not use a tray detection means, it is common practice to removably mount on the printing apparatus a member for guiding and supporting the tray as it is loaded into the printing apparatus (in this example, the member is described as a CD transport unit) and check whether this member is mounted on the apparatus. In this configuration, however, whether the tray is loaded in an appropriate position in the apparatus may not be able to be detected correctly. Thus, when a tray is loaded in the printing apparatus, the tray may be set very close to a carriage in the apparatus depending on the loaded position of the tray. Therefore, when a print head and an ink tank mounted on the carriage are to be removed or replaced by moving the carriage to a position opposing the transport path loaded with a CD mounting tray, ink adhering to the print head or carriage may come into contact with and contaminate a print medium such as the CD or its tray.
(2) To solve the above problem, a carriage setting position (replacement position) where a print head and an ink tank are replaced may be set outside the transport path of the print medium including CD and tray. However, the transport path is generally provided almost at a center of the printing apparatus with respect to a carriage scan direction. Therefore, to set the replacement position outside the transport path requires forming an opening at an end portion of the equipment case. This reduces the strength of the case, giving rise to another problem.
(3) Further, as described in (1) above, the configuration that does not detect the loading of a print medium, such as a CD mounting tray, into the transport path has a drawback that, during the cleaning operation performed prior to the printing operation, if the carriage moves across the print medium transport path, ink adhering to the print head and carriage may contact and contaminate a print medium, such as CD and tray.